The invention relates to a hammer drill comprising an electric drive motor, a tool shaft that is driven in rotation by the drive motor, and a hammer action.
Hammer drills of known configuration for hand-held operation have a drive motor, a tool shaft driven in rotation by the drive motor as well as a hammer action. The drill bit clamped in a chuck is rotated by the tool shaft. The drive motor that drives the tool shaft actuates also the hammer action that exerts axial hammer strokes on the drill bit. When drilling into stone or similar materials, the drill bit produces a drill hole by simultaneous action of the drill bit rotation and the axial hammer strokes.
For generating the combined rotation and hammer stroke action, in hammer drills according to the prior art a second shaft is provided parallel to the tool shaft. The tool shaft is driven via a two-stage gear unit by the drive motor. The drive motor operates by means of a first gear stage the additional shaft that, in turn, drives the tool shaft by means of a second gear stage. The intermediately positioned second shaft serves moreover as a drive for the hammer action.
The parallel arrangement of two shafts, i.e., the tool shaft and the drive shaft of the hammer action, requires significant mounting space. The same holds true also for the two-stage gear. The configuration is large, heavy and cost-intensive.